Application of granulosis virus (CPGV) to plots of apple trees reduced deep-entry damage to apples by the codling moth, Cydia pomonella (L.), compared with nontreated apples. However, shallow-entry damage to apples by codling moth was as great, or greater, in virus-treated plots than in nontreated plots. Protection was improved by applying CPGV at least three times during each of the two annual generations of the codling moth compared with less frequent application.Bioassays showed that activity of deposits of CPGV on apples in the field was reduced to approximately 50% of original activity within 2 days after application and to 17% by the 10th day.
Habrobracon lineatellae Fischer has been imported from Lebanon into California in the course of a project on the biological control of the peach twig borer, Anarsia lineatella (Zeller). The navel orangeworm, Paramyelois transitella (Walker), is used as a host to mass-culture this parasite. Its biology is similar to that of other species in the genus, for the female paralyzes the host before oviposition and the larvae develop ectoparasitically. Females begin to paralyze hosts 2 to 26 days after emergence, and oviposition is initiated 1 day after they begin this host paralyzation. The number of eggs per female varies from 32 to 954. A maximum of 12 larvae of H. lineatellae can develop on 1 larva of P. transitella. When virgin females are held for 4 days and then placed with sexually active males for the rest of their lives, the sex ratio of the progeny is 53% female. The adults do not host feed. Females fed honey–water live an average of 105 days (range 51 to 166 days).
The efficacy of mixtures of chlordimeform with Bacillus thuringiensis and(or) Autographa californica nuclear polyhedrosis virus and Pieris rapae granulosis virus against Trichoplusia ni and Pieris rapae on the late cabbage was assessed in field plots over four growing seasons. Mixtures of 0.07 kg of chlordimeform/ha (1/8 of the recommended dosage) with low concentrations of the microbial insecticides were as effective or more effective than the materials used alone at full rates. The advantages of such mixtures in pest management are discussed.
The control of the Colorado potato beetle, Leptinotarsa decemlineata (Say), by formulations of Bacillus thuringiensis (Berliner) (B.t.) and other microbial agents and chemical insecticides was assessed in field plots of potatoes and tomatoes over a 5-year period. Applications of formulations of thuringiensin, the beta exotoxin of B.t., and of B.t. var. son diego (B.t.sd.) to potatoes reduced numbers of larvae of the potato beetle compared with the nontreated check and resulted in yields significantly greater than from the check plots and, in most cases, similar to yields from plots treated with carbofuran. Treatment of tomatoes with B.t.sd. reduced populations of larvae of the Colorado potato beetle compared with the nontreated check and increased yield of nondamaged fruit from plots. An initial application of carbofuran to potatoes or permethrin to tomatoes followed by applications of thuringiensin or B.t.sd. protected potatoes or tomatoes as well as did the chemical insecticide used alone in a treatment program. Applications of preparations of B.t. var. kurstaki or spores of the fungus Beauveria bassiana (Balsamo) Vuillemin or the microsporidium Vairimorpha necatrix (Kramer) did not reduce populations of the beetle.
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